The present invention relates to a coating film forming method and a coating film forming apparatus for coating a process liquid such as a photoresist liquid on a substrate such as a semiconductor wafer or an LCD glass substrate to form a coating film.
In manufacture of a semiconductor device, a photoresist liquid is coated on a semiconductor wafer to form a photoresist coating film, the photoresist coating film is exposed and then developed. Such a photolithography technique is a very important process in high integration of a semiconductor device. In order to uniformly form a photoresist film on a wafer surface in this process, the closest attention is paid, and a long period of time is spent.
As shown in FIG. 1, a conventional resist coating apparatus comprises a process vessel 2, a spin chuck 3, a cup 4, a resist liquid supply nozzle 5, a fan filter unit (FFU) 6, a temperature/humidity adjustment device 7, a temperature/humidity sensor 9a, and a controller 9. The process vessel 2 is partitioned from the atmosphere of a wafer convey section 1 by a panel. A spin chuck 3 is arranged in the process vessel 2. The spin chuck 3 vertically moves along a Z axis to be able to rotate about the Z axis by .theta.. The cup 4 is arranged to surround the outer periphery and lower portion of the spin chuck 3, and a gas outlet port 4a and a liquid outlet port 4b are formed in the bottom portion of the cup 4. The resist liquid supply nozzle 5 is designed to discharge (supply) a resist liquid toward a wafer W held on the spin chuck 3. The FFU 6 comprises a fan 6a and a filter 6b for supplying clean air into the process vessel 2. The temperature/humidity adjustment device 7 is designed to adjust the temperature and humidity of the air in the process vessel 2. The temperature/humidity sensor 9a is arranged near the FFU 6 and connected to the input side of the controller 9.
In the resist coating apparatus arranged as described above, a wafer W is conveyed into the process vessel 2 by the convey arm mechanism 8, is held by adsorption of the spin chuck 3, and is spin-rotated. A resist liquid is supplied from the nozzle 5 to the wafer W while the wafer W is spin-rotated to coat a resist on the wafer W. Furthermore, the spin chuck 3 is rotated at a high speed, a resist liquid is uniformly diffused on the entire surface of the wafer W to form a resist coating film having a desired thickness. During this process, the temperature and humidity of the internal atmosphere of the process vessel 2 are detected by the temperature/humidity sensor 9a, and these detection signals are sent to the controller 9. The temperature/humidity adjustment device 7 is controlled by the controller 9 to supply clean air whose temperature and humidity are adjusted from the temperature/humidity adjustment device 7 into the process vessel 2, so that the process atmosphere is kept in a desired state. After the resist coating film is formed as described above, the rotating speed of the spin chuck 3 is reduced, and thinner is poured onto the rear surface of the wafer W. The wafer is rotated at a high speed again, the thinner and coated resist are centrifugally removed from the rear surface of the wafer W.
However, in the conventional coating film forming apparatus, the temperature/humidity adjustment device 7 outside the process station, and the temperature/humidity adjustment device 7 is connected to the coating film forming apparatus through a pipe 7a. For this reason, the apparatus increases in size.
When only the temperature and humidity of the processing atmosphere are adjusted, not only the film thickness cannot be made uniform at high precision, but also air whose humidity is adjusted is forcibly supplied. For this reason, air flow in the processing atmosphere is disturbed, and the uniformity of the film thickness is adversely affected.